Electronic games commonly use three dimensional modeling, animation and rendering techniques to achieve realistic characters, playing environments and interaction. Some electronic game platforms, such as the Sony PLAYSTATION Nintendo GAMECUBE and Microsoft XBOX game consoles, have “engines” which render three-dimensional animations in real time during play, i.e., at runtime. Example game engines include, but are not limited to, Source from Valve and Unreal from Epic.
These game engines generally represent a character as a skeleton with an associated envelope or skin to which color and textures are applied using a process called shading. A skeleton typically is defined by a set of interconnected or related bones. The envelope or skin typically is defined as a three-dimensional mesh. A set of envelope weights or skinning weights defines the relationship between bones in the skeleton and the vertices in the mesh defining the envelope or skin. The process of defining these weights is called skinning. Animation is applied to the skeleton. The set of envelope weights determines how the mesh deforms in response to movement of the skeleton. A set of normal maps affects how shading is applied to the mesh. The envelope weights and normal maps can be animated over time.
When games are developed, various three-dimensional modeling, animation and rendering tools are used by artists to define the characters and the environments of the games. Typically, these artists work with models with a higher resolution than the resolution used in the game engine. Further, a tool used for creating a model or animation may represent characters and animation in a way that is different from the representation used in the game engine. In particular, if the representation of motion, deformations and shading of the mesh in the tool is different from the representation in the game engine, the representation of the characters and animation needs to be converted to a representation that can be used by the game engine.